The ornamental design for a revetmentblock, as shown and described.
FIG. 1 is a perspective view of a revetment block according to my new
design, the broken line showing of additional revetment blocks encased in
a fabric sheet is for illustrative purposes only and forms no part of the
claimed design;
FIG. 2 is a left side elevational view thereof, the right side being a
mirror image thereof;
FIG. 3 is a front side elevational view thereof, the back side elevational
view being a mirror image thereof; and,
FIG. 4 is a top plan view thereof, the bottom plan view thereof.